This invention relates to digital video and more particularly to coding efficiency of high definition (HD) video data.
Motion compensated prediction (MCP) is the key to the success of modern video coding standards. With MCP, the video signal to be coded is predicted from the temporally neighboring signals, and only the prediction error and the motion vector (MV) are transmitted. However, due to the finite sampling rate, the actual position of the prediction in the neighboring frames may be out of the sampling grid, where the intensity is unknown, so the intensities of the positions between the integer pixels, called sub-positions, must be interpolated and the resolution of the MV must be increased accordingly. In the existing video coding standards, the interpolation filter is designed to fit the general statistics of various video sources, so the filter coefficients are fixed.
In prior work, adaptive interpolation filter (AIF) techniques have been used wherein the coefficients are analytically calculated for each frame using a linear minimum mean squared error (LMMSE) estimator. However, AIF techniques code the filter coefficients individually, and therefore trade-offs between the accuracy of coefficients and the size of side information must be made. These two conflicting aspects are the major obstacles to improving the performance, as inaccurate coefficients greatly degrade the performance of the interpolation filter.
Due to higher data rates associated with HD video coding, there is a need to improve the coding efficiency of HD video.